Adding GSSPROXY_CONF to be backed up on ipa-backup
Without GSSPROXY_CONF being backed up, we would get this error
"ipa: ERROR: No valid Negotiate header in server response"
when running any ipa command after a backup restore.
This commit also fixes the tests:
- TestBackupAndRestore::test_full_backup_and_restore
- TesttBackupAndRestore::test_full_backup_and_restore_with_selinux_booleans_off
https://pagure.io/freeipa/issue/7473
Reviewed-By: Christian Heimes <cheimes@redhat.com>